Researchers measured the sperm counts of more than 600 men in order to study the negative effects of cannabis on male fertility. What's more, all the of the men were enrolled at a fertility clinic, meaning they were seeking medical help with their partners to try to get pregnant.
For the new study, investigators collected 1,143 semen samples from 662 men between 2000 and 2017.
The research showed 55 per cent of the men had tried cannabis in the past and 11 per cent said they were current users.
Out of those who reported to have been using bhang, only 5% had sperm counts below 15 million/ml, the threshold for normal levels as per the World Health Organisation. Now, researchers at Harvard have found an unexpected side effect of smoking pot - it appears to increase sperm count.
"We know a lot less than we think we know", said the associate professor of nutrition and epidemiology at Harvard University.
However, Chavarro noted that some of those past studies surveyed men who use multiple drugs at once, making it hard to pinpoint the effects of marijuana alone. The men answered survey questions about how often they smoked marijuana or used other drugs, and they also provided sperm and blood samples.
The men who admitted to smoking marijuana at some point in their life seemed to have higher concentrations of sperm than those who had never had a puff.
Nevertheless, because much of this research is based on animal models and those with histories of drug abuse, the average pot smoker still can't be sure there's anything sinister to worry about.
"An equally plausible interpretation is that our findings could reflect the fact that men with higher testosterone levels are more likely to engage in risk-seeking behaviours, including smoking marijuana". Second, because the study's sampling wasn't diverse - 88% of the men were Caucasian, 84% were college educated, and the average age was 36.3 years old - the results may not apply to the general population.
Scientists analysed the sperm quality of regular cannabis smokers as well as non-smokers, with some unexpected results. Among marijuana smokers, the researchers found greater use was associated with higher serum testosterone levels.
Feiby Nassan, lead author of the study and a postdoctoral research fellow at Harvard Chan School, told Newsweek: "Because the endocannabinoid receptors (the ones responsive to marijuana) are found in many places in the body especially the reproductive system, we need to understand their role on our health, especially with increasing their legalization".
Chavarro also went on to point out that if the study proves anything definitive, it is that the link between marijuana and general health remains something of a grey area.
'In my opinion, this should be avoided at all costs in any couples trying to start a family'.